Rough runner after oxygen sensor replacement
 

My 2000 Camry 2.2 L showed a CHECK ENGINE light last week. My mechanic found code P1135, and replaced the front oxygen sensor yesterday (he used a DENSO brand). Check engine light is now off. Last night I drove 45 miles to a concert, mostly at 60 miles per hour, and the engine often "stumbled", both while accelerating and at steady speed, but the light stayed off. On the trip home it was a bit better, but not great. And of course my mechanic left on vacation today. And idea what may may be going on, and what can be done to smooth things out?

Did the engine have any performance issues (other then the check light on) prior to the sensor replacement?

Could be the wrong sensor was used or something was unplugged, damaged, etc. during the repair.

The check engine system runs the same test several times to confirm a problem before the light comes on. It's possible the check system has not completed all it checks.

If the check light does comes on and ever starts to blink, stop driving the car. A blinking check light means the misfire is so bad it can cause damage to the emissions converter.